It has been long recognized that fresh water is a very valuable commodity in ocean going vessels. As a result, fresh water is utilized as sparingly as possible and, in some instances, the readily available sea water is utilized. As an example, it is common practice to use raw sea water as the cooling medium in marine engine heat exchangers. This sea water can, in some cases, have a detrimental effect upon the circulatory systems of marine engines because of electrolysis and corrosive effects on metal parts.
In addition, in spite of the diligence of the captain in navigating the boat away from debris in the ocean, it is not uncommon for the sea water ingested into the circulatory system of the vessel to contain debris of various types which can mechanically damage components of the system. Thus, it is recognized that it would be desirable to have an apparatus for reducing, or in some cases, eliminating the unwanted effects of raw sea water in marine circulatory systems in which sea water is utilized for cooling.
In a typical marine heat exchanger, an impeller having hardened rubber blades is utilized to drive the raw sea water through the heat exchanger. Water borne debris introduced into the raw water system can obstruct water passage therethrough, thereby disabling the pump.
Further, in such cases, larger forms of debris can damage the impeller blades when the pump runs in a dry condition. In addition, portions of the blades can break off and these portions, in turn, can significantly damage the heat exchanger. In such cases, where loss of heat exchanger function occurs, engine failure with such unwanted consequences as the necessity of rescue at sea and the expenditure of substantial amounts of money can be experienced. Thus, it would be highly desirable to have an efficient and effective technique for monitoring heat exchanger operation to foreclose damage caused by impeller blade debris. Ideally, such a technique would provide an indication of imminent heat exchanger damage and, in some cases, would function so as to prevent damage to the heat exchanger.
Devices for monitoring the function of mechanical systems are known. For example, in U.S. Pat. No. 2,756,680, there is disclosed a transparent glass plate in an electric motor driven pump wall which enables one to observe pump shaft rotation and direction. Such an arrangement has utility in land based systems but is very limited in confined marine spaces where the marine inboard engine is located. U.S. Pat. No. 3,135,214 discloses a pump attachment for outboard motors located downstream of a propeller. A filtering screen allows passage of water while preventing the passage of objects. While such an arrangement has some value, this device gives no indication of whether or not the pump itself is functioning. In this regard, heat exchanger failure could occur while the pump attachment would give no indication of imminent trouble.
U.S. Pat. No. 5,197,909, there is disclosed an indicator structure for informing an outboard motor operator that the water pump is functioning. Colored flotation members are driven through an upper chamber having a transparent wall for providing a visual display of pump operation. The upper chamber is separated from a lower chamber by a perforated plate which confines the flotation members to the upper chamber while permitting fluid communication between the two chambers. The device has a limitation of being located at some distance from the outboard engine, thus requiring that it be plumbed to the outboard motor water pump exit.
In general, conventional devices are bulky and, in some cases, expensive and not readily adaptable to the marine environment. In addition, while they may afford some sensible indication of engine function, they do not provide a direct capability for preventing damage to engine components. Thus, the prior art fails to disclose an inexpensive pump monitoring apparatus which could be readily installed on marine engines, in confined spaces, and Which could provide a continual real time indication of marine engine conditions while also having a direct damage preventing capability.
In addition to the effects of the unwanted debris in the raw water stream, it is recognized that the electrolytic effect of the raw sea water must be carefully observed in order to avoid irreversible damage to metal parts. In this regard, the use of sacrificial materials, such as zinc anodes, are known. In these cases, the anode material is consumed as a result of galvanic action and, as long as a sufficient amount of such material is available, other metal parts are protected. In this regard, reference may be made to U.S. Pat. Nos. 800,296; 2,523,443; 3,037,920; 3,406,110; 3,423,305; 4,051,007 and 4,789,363. In general, these patents disclose various types of cathode protective materials which, in some cases, are bulky, expensive and ill suited to the confined spaces of ocean going vessels. In addition, such devices sometimes require expensive special housings.
Another limitation to the use of sacrificial anodes is that they are sometimes located in inaccessible areas so that inspection of anode condition is accomplished by a diver or when the boat has been hauled out of the water for maintenance and repair. Thus, for several reasons, anode condition can be difficult to determine. In this regard, unobserved anode deterioration can occur and portions of the anode can break away to be carried by the liquid stream to a heat exchanger or engine component where the portions can obstruct liquid flow, thereby causing damage. Thus, a need exists for a technique for regularly and conveniently assessing anode condition.
In view of the foregoing, it would be highly desirable to have an inexpensive, efficient marine engine monitoring apparatus which would be readily installed and conveniently maintained, even in confined marine engine spaces. Such an apparatus would provide a capability for continual monitoring of flow through the raw water cooling system and would provide a ready indication of the presence of debris in the line. Because of its monitoring applications, such an apparatus could function prophylactically to help prevent marine engine damage while, at the same time, providing a system monitoring capability.